US President Barack Obama has become the first sitting US leader to visit the isolated south-east Asian nation of Laos.

Mr Obama exited the main door of Air Force One clutching a black umbrella in the evening rain in the capital Vientiane, before a motorcade whisked him away.

The visit comes during what is probably Mr Obama's final trip as president to south-east Asia, a region that has enjoyed intense attention from the US during his tenure.

In Laos, Mr Obama will wrestle with the ghosts of past US policies as he meets leaders of the Association of South-East Asian Nations.

In the 1960s and 1970s, the US rained bombs on Laotian villages and the countryside as America's war with Vietnam spilled across the border.

The Laotian government estimates that more than two million tons of ordnance were released during more than 500,000 missions - one bomb every eight minutes for nine years.

An estimated 80 million cluster bombs did not explode, leaving tennis ball-sized "bombies" littering the impoverished countryside to wound and kill unsuspecting people.

Mr Obama planned to acknowledge this history and its damaging effect on Laos' development, tourism and agriculture.

He is expected to announce additional aid to clean up unexploded ordnance, while the Laotian government is expected to offer help in accounting for missing and dead US service members.

Mr Obama said on Monday in China, before he departed for Laos, that diplomatic work on war legacy issues will be "a show of good faith on the part of the country and a way for us to move into a next phase of a relationship".

He cited Vietnam as the model. Aides said Mr Obama's visit will probably echo a stop in Hanoi, Vietnam, in May, when the president declared he was "mindful of the past, mindful of our difficult history, but focused on the future".

In both countries, Mr Obama benefits from not carrying baggage that might have complicated his message. Too young to have served in the Vietnam War, he serves as a generational page turner - eager to speak directly to those too young to remember the troubled past.

In Laos, as he has across south-east Asia, he will hold a town hall-style event for young people. The White House said he will encourage Laos' slow political opening and budding entrepreneurial culture.

While the US is known as a rich country with an outsized cultural influence, China, by contrast, is seen as the huge neighbour helping to spur this small nation's robust growth. Massive Vientiane construction sites come adorned with Mandarin script. China has committed to financing a 7 billion US dollar (£5.3 billion) high-speed railway to bisect the country.

Though Laos' new president, Bounnhang Vorachit, is seen as edging closer to Vietnam than to China, the country has managed a diplomatic two-step this year. As chair of the Association of South-East Asian Nations group this year, it has projected neutrality in other countries' disputes with China over the South China Sea.